Bolt sleeve expanded by wedge and wedging threads



Aug. 3, 1954 L .,BARRETT 2,685,221

BOLT SLEEVE EXPANDED BY'vWEDGE AND WEDGING THREADS Filed oct. e, 1949 l 2 sheets-sheet' v1 QZZarzzey Aug. 3, 1954 A, L, BARRETT 2,685,221

BY WEDGE AND WEDGING THREADS BOLT SLEEVE EXPANDED Filed oct. 6, 1949 2 Sheets-Sheet 2 y la zveziozg;

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Patented Aug. 3, 1954 BOLT SLEEVE EXPANDED BY WEDGE AND WEDGING THREADS Arthur Lee Barrett, Franklin, Pa., assignor to Joy Manufacturing Company, Pittsburgh, Pa., a corporation of Pennsylvania Application October 6, 1949, Serial No. 119,835

. Claims. l

This invention relates to suspension type roof supports and particularly to expansible anchor bolts insertable in holes drilled in the roof strata for supporting cross beams or plates against the roof, to prevent roof failure due to rock fracture.

In suspension type supports employed to support the roof of a mine passageway or other subterranean excavation, cross beams or plates are usually secured by anchors set in holes drilled in the roof strata, thereby eliminating the necessity of conventional external timbering. In roof anchors of known types there is a possibility of slippage of the anchors in the holes particularly when the roof settles and further some diculty presents itself in the insertion of the bolts into the holes and for maintaining the same in position during expansion of the bolt heads. In known types of anchor bolts it is necessary to employ a section of pipe to effect insertion of the bolt into the hole and for holding the'bolt in position during head expansion. In such bolts when the heads thereof are set in position in the holes there is a possibility of the heads becoming loosened since there is n0 provision for effecting further automaticexpansion of the bolt heads. The present invention contemplates improvements over such known types of bolts in that not only are the bolts rmly anchored kin holes drilled in the roof strata but also any increased load on the bolts, such as may be due to settling of the roof, tends to eiTect increasein the expansion of the bolt heads thereby to eiiect firm anchoring of the bolts. Also, the bolts of the present invention may be easily inserted in the holes drilled in the roof strata without the Vneed of a special tool and may be readily maintained in position during expansion of the bolt heads. The bolt oi .the present invention has threads for initially affecting expansion of the bolt head upon rotation of the bolt and a -coacting wedging structure for further expanding the bolt head upon axial non-rotative downward movement of the bolt.

An object of the present invention is to provide an improved suspension type roof support for mine passageways or other underground workings. Another object is to provide an improved expansible anchor bolt. A further object is to provide an improved roof bolt structure having an improved expansible head for gripping the walls of a hole drilled in the roof strata. A still further object is to provide an improved ex- Apansible roof bolt which may be easily and quicka screw and nut structure for initially expanding the bolt head and a coacting wedge structure for further expanding the head, so that firm anchoring of the bolt is attained." These and other objects and advantages of the invention will, however, hereinafter more fully appear.

In the accompanying drawings there are shown for purposes of illustration two forms and a modiication which the invention may assume in practice.

In these drawings:

Fig. 1 shows a section of roof strata with an illustrative form of the improved anchor bolt inserted in a hole drilled in the strata, with the bolt head in initially expanded position.

Fig. 2 is a sectional view similar to Fig. 1 showing the anchor bolt in fully expanded position in the hole.

Fig. 3 is an enlarged side elevational view, with parts shown in central longitudinal section, of the anchor bolt shown in Figs. 1 and 2.

Fig. 4 is an enlarged fragmentary sectional view taken on the plane of Fig. 3, with the bolt head in fully expanded position.

Fig. 5 is an enlarged cross sectional view taken on line 5 5 of Fig. 3.

Fig. 6 is an enlarged view in side elevation showing a modied form of expansible bolt head.

Fig. 7 is a cross sectional view taken on line 'l-i of Fig. 6.

Fig. 8 is a diagrammatic cross sectional view taken through a mine passageway `or tunnel showing a cross beam or plate secured against the roof by the improved anchor bolts.

Fig. 9 is a sectional view through the roof strata showing another form of anchor bolt secured in a hole drilled in the strata, with the bolt head in partially expanded position.

Fig. l0 is a sectional view similar to Fig. 9, showing the anchor bolt in fully expanded position.

Fig. 11 is an enlarged side elevational view, .with parts in central longitudinal section, of the anchor bolt shown in Figs. 9 and 10.

Fig. 12 is an enlarged cross sectional view taken on line iZ-IZ of Fig. l1.

Fig. 13 is an enlarged sectional view taken on line I3-I3ofFig-l1.

Fig. 14 is an enlarged sectional View takenon the plane of Fig. 11, showing the bolt head in fully expanded position in a hole.

Fig, 15 is a diagrammatic view similar to Fig. 3, showing a cross beam or plate held against the roof by the modified form of anchor bolts.

In the illustrative embodiment Vof the invention shown in Figs. 1 to 5 inclusive the anchor bolt is generallydesignated l and is insertable in a hole 2 drilled in the rock strata and engages a cross beam or plate 3 for securing the latter in supporting position against the roof. The

anchor bolt has an elongated rod-like body 4 which at its lower end is externally threaded at 5. The upper end of the bolt body is formed with a wedge portion 6 and below this wedge portion the body is externally threaded at 1. The threads 'I may be of the modified buttress type having downwardly tapering external surfaces 8 and the external taper of the threads may desirably be the same as the external taper of the the upper wedge portion l. A split bushing consisting of a pair of cooperating gripping plates or segments 9 of substantially semi-circular cross section surrounds the upper portion of the bolt body and the segments have internal threads It which engage the bolt-threads 'l as clearly shown in Fig. 4. The threads IB have upwardly tapering surfaces H which engage the tapering thread surfaces 8 and the upper portions of the gripper plates are internally tapered at Il' to provide wedging surfaces with which the wedge portion E is adapted to engage. as later explained. Instead oi the two part grip-- ping plate structure an expansible sleeve l2 (Figs. 6 and 7) longitudinally split along one side at I3 may be employed. The split sleeve i2 may substantially fit-the hole drilled in the roof strata so that the same may be frictionally held in contact with the hole-walls. The gripper plates 9 may be externally annularly grooved at I4 to receive snap rings, contractile wire springs or other friction devices l5 to provide sufficient friction between the gripping plates and the walls of the hole so that when the bolt is rotated the plates may be expanded into gripping Contact with the hole-walls.

The gripping plates 9 of the split bushing are held contracted by the snap rings or springs i5 in engagement with the bolt-threads 'l and are supported by the threads when the bolt is inserted in the hole and moved upwardly to locate the expansible bolt head at the hole bottom as shown in Fig. 1, and the bolt may then be suitably rotated to eiect axial movement of the wedge portions S thereby to cause the threads initially to expand or spread apart the gripper plates into gripping engagement with the holewalls. The cross beam or plate 3 may then be placed against the roof, angle washers l@ may be placed over the projecting end of the bolt a nut l? may be threaded onto the threaded end 5 of the bolt and when tightened the bolt is drawn downwardly without rotation to cause the wedging surfaces of the threads and the wedge portion t to further expand the bolt head and to clamp the cross beam or plate firmly against the roof. If the roof tends to settle, any additional axial downward pressure imparted to the bolt causes further wedging of the head to effect further tightening of the anchor. By moving the bolt upwardly and rotating the same in the opposite direction, the bolt-head may be readily contracted, to permit removal of the bolt from the hole.

Now referring to the embodiment shown in Figs. 9 to l5 inclusive it will be noted that the anchor bolt is generally designated 2li and includes a rod-like bolt portion 2l having its lower end externally threaded at 22. The upper end of the bolt is formed with a wedge portion 23 and the bolt body below the wedge portion 23 is externally threaded at 24. Surrounding the upper portion of the bolt is a split expansible sleeve 25 which is longitudinally split at 25 to provide laterally bendable iinger-like portions 2l, which are internally tapered at 28. It desired the sleeve may assume the forni of a pair. of cooperating semi-circular gripper plates or segments as in the embodiment above described. Secured in any suitable manner to the bottom of the sleeve is a spring steel clip 29 having spring fingers 3) Vwhich engage the threads 24 in the same manner as a nut engages a screw. The split sleeve is annularly grooved at 3| about its periphery to receive a wire contractile spring 32 for urging the spring fingers toward their contracted position.

In use the split sleeve is held on the upper end of the bolt by the spring clip engaging the threads 24 and the bolt is inserted in the hole and moved upwardly to locate the'expansible bolt head near the bottom of the hole as shown in Fig. 9. The bolt may then be suitably rotated to cause the threads 24 to work downwardly along the spring clip to bring the wedge portion 23 in engagement with the tapered surfaces 28 of the fingers to spread the latter apart into firm gripping engagement with the walls of the hole. The cross beam or plate 3 may then be placed against the roof, and the nut Il' may be threaded onto the threaded end 5 of the bolt, and when tightened the bolt is drawn axially downwardly without rotation to cause the wedge portion 23 to further expand the bolt head thereby to clamp tightly the beam or plate against the roof. If the roof tends to settle any additional pressure imparted to the bolt effects further drawing of the wedge portion downwardly within the split sleeve further to expand the spring finger portions, thereby to eiect firm anchoring of the bolt. By moving the bolt upward and rotating the bolt in the opposite direction, the bolt may be readily released.

In both embodiments the holes 2 drilled in the roof strata may be relatively inclined as shown in Figs. 8 and 15 and the cross beams or plates 3 may extend along the roof substantially the full width of the mine passageway or tunnel with the lower projecting ends of the anchor bolts extending through suitably located holes in the beams or plates and when the bolts are tightened by the nuts threaded on the bolt-ends the cross beam or plate is firmly secured in supporting position against the roof. Evidently, the holes drilled in the roof strata may be vertically or otherwise disposed and, in certain instances, in lieu of continuous cross beams or plates the anchor bolts may be provided with individual roof engaging plates. Under certain conditions the lower projecting ends of the bolts may be headed or bent over directly against the roof without the use of either cross beams or plates.

As a result of this invention an improved suspension type roof support for a mine passageway or other subterranean excavation is provided whereby the roof is supported wholly without the use of conventional external timbering. .The improved anchor bolts by the provision oi the novel expansible head structures may not only be initially tightened into gripping engagement with the walls of the holes but may be further automatically tightened as the load on the bolts increases, as for example, due to settling of the roof. By the provision of screw threads and the coacting wedge structure the bolts when suitably rotated may be initially expanded and upon axial non-rotative movement of the bolts in a downward direction the bolt heads may be further tightened. Thus, the possibility of slippage of the anchor bolt in the hole is substantially reduced. Due to the novel expansible head structure of lthe anchor bolts the bolts may be readily inserted in the holes drilled in the roof strata without the need of special tools, and may be readily released when desired. Other manners of use and advantages of the invention will be clearly apparent to those skilled in the art.

While there are in this application specifically described two forms and a modification which the invention may assume in practice, it will be understood that these forms of the same are shown for purposes of illustration and that the invention may be further modified and embodied in various other forms without departing from its spirit or the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent is:

l. A suspension type roof support insertable in a hole formed in roof strata to be supported, comprising an elongated bolt body having an externally threaded portion and a wedge portion providing a tapered wedging surface and spaced axially of the body from said threaded portion, and a split expansible sleeve surrounding said body and having internal threads providingr a nut and rotatively and slidingly engaging the threads of said threaded portion, said sleeve also having tapered internal surfaces with which said tap-ered surface of said wedge portion is engageable, said threads having coacting tapered surfaces of the same inclination as the tapered surface of said wedge portion so that said coacting tapered thread surfaces may in themselves produce a wedging action as they slide relative to each other upon axial non-rotative movement of said bolt relative to said sleeve, said bolt body, upon rotation relative to said sleeve, causing said bolt-threads to act on said nut-providing threads on said sleeve to move said wedge portion axially relative to said sleeve initially to expand the latter, and said wedge portion, upon non-rotative axial movement of said bolt body relative to said tapered surfaces of said sleeve, moving further axially within said sleeve for effecting further expansion of the latter.

2. A suspension type roof support insertable in a hole formed in roof strata to be supported, comprising an elongated bolt body having an upper end wedge portion providing a tapered wedging surface and external threads on said body below said wedge portion with the outer surfaces r said tapered surface of said wedge portion is engageable and nut-providing elements rotatively and slidingly engaging said external thread surfaces of said sleeve, said nuteproviding elements, upon rotation of said bolt body relative to said sleeve, cooperating with said bolt-threads to effect axial movement of said bolt body to cause said tapered surface of said wedge portion to move within and engage said internal tapering surfaces to expand said sleeve into initial gripping engagement with the walls of the hole, and said wedge portion and said coacting internal surfaces cooperating to effect, as they slide relative to each other upon axial nonrotative movement of said bolt body in one direction relative to said sleeve, further expansion of said sleeve firmly to anchor the bolt in the hole.

ill

3. A suspension type roof support insertable in a hole formed in roof strata to be supported, comprising an elongated bolt body having an up- Der end wedge portion providing a tapered wedging surface and external threads on said body below said wedge portion with the external surfaces of said threads tapering downwardly, the taper of said external thread surfaces being of the same angle as said tapered surface of said wedge portion, an expansible split sleeve surrounding said body and having internal threads providing a nut and having internal tapering surfaces rotatively and slidingly engaging said external tapering thread surfaces of said bolt, said nut-providing threads, upon rotation of said bolt body relative tosaid sleeve, effecting axial movement of said wedge portion to cause expansion of said sleeve into initial gripping engagement with the walls of the hole, and said wedge portion and said coacting thread surfaces as they slide relative to each other cooperating to effect, upon 4axial non-rotative movement of said bolt body in one direction relative to said sleeve, further expansion of said sleeve firmly to anchor the bolt in the hole.

l. An expansible anchor bolt insertable in a hole formed in the strata to be supported, comprising a bolt body having a threaded portion and an axially spaced wedge portion providing a tap-ered wedging surface, the threads of said threaded portion having tapering surfaces of the same inclination as said tapered wedging surface, and an expansible split sleeve surrounding said bolt body and adapted tightly to grip the walls of the hole, said sleeve having internal threads providing a nut and rotatably and slidingly engaging said threaded portion and spaced axially from its threaded portion internal tapering surfaces with which said tapered surface of said wedge portion is engageable, said cooperating nut-providing threads and threaded portion causing, upon rotation of said bolt body relative to said sleeve, axial movement of said wedge portion relative to said tapering sleeve surfaces for initially expanding said sleeve, and said cooperating threads and said threaded portion having relative axial sliding movement, upon non-rotative axial movement of said bolt body relative to said sleeve, to cause further expansion of said sleeve.

5. An expansible anchor bolt as set forth in claim 4 wherein spring means encircling said sleeve is provided for urging said sleeve toward contracted position, said sleeve being expansible as aforesaid against the action of said spring means, and said spring means being embedded into the hole walls upon such further expansion of said sleeve.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date Re. 22,926 Tinnerman Oct. 7, 1947 781,110 Stulz Jan. 31, 1905 895,158 Caputo Aug. Ll, 1908 1,523,463 Thomson Jan. 20, 1925 2,386,732 Wohlhieter Oct. 9, 1945 FOREIGN PATENTS Number Country Date 476,982 France Sept. 15, 1915 827,301 France Apr. 25, 1938 569,774 Great Britain June 7, 1945 

